Process of hydrogenating crotonic aldehyde



Patented Aug. 13, 1929. 7 I

UNITED STATES 1,724,161 PATENT ornca.

. nnum CHESTER HOLDEN, OF ELMHURST, NEW YORK, ASSIGNOB. TO CARBIDE AND CARBON CHEMICALS CORPORATION, A. CORPORATION OF NEW YORK.

PROCESS OF HYDROGENA'IING CROTONIC ALDEHYDE.

Io Drawing.

(1) Clh-CHK'JILCIIO B1 CIIrCHrClIrCHO crotonlc aldehyde butyraldehyde (2) CIh-CIh-CHg-CIIO H, CHvCII -OIh-CILOII butyraldehyde butyl alcohol The hydrogenation takes place without special difliculty in the presence of catalysts, such as nickel, throughout a considerable range of temperatures.

Such processes have been nvestigated to some extent but on attempting to recover the butyraldehyde and butyl alcohol from the products of hydrogenation, prior workers have found that a considerable proportion of the raw material had become converted into undesired high-boiling substances, supposed to consist, in whole or 1n part, of octyl alcohol or d1butyl butylal.

In order to revent the formatlon of these undesired products, it has been proposed to carry out the hydrogenation in the presence of steam. This expedient is effective to some extent, though my investigations lead me to believe that the greater part of the improvement thus obtained is due to conditions incidental to the presence of steam in the hydrogenating zone, rather than directly dependent upon it. Moreover, the steam dilutes the reacting materlals and thereby decreases the rate of hydrogenation.

I have found that the hydrogenation may be effected in the absence of steam, and the formation of serious quantities of undes red high-boiling products nevertheless avoided by carrying out the process m a manner now to be described. In accordance with my 1nvention, it is possible to obtain better yields than in the prior processes, and other advantages may also be secured.

One important source of loss of material in the process appears to be the decomposition of the crotonic aldehyde in the hydrogenating apparatus, such loss increasing with the temperature. The hydrogenation of crotonic aldehyde requires only moderate temperatures, and after most of the compound has been converted, further quantlties of the resulting butyraldehyde can be hydrogenated to butyl alcohol at higher temperatures, for example between 160 C. and 180 C., the concentration of crotonic Application filed January 8, 1923. Serial No. 811,518;

aldehyde in the higher temperature zones being too low to result in serious loss through its decom )osition. For this reason I prefer to keep the temperature in the hydrogenating apparatus below 140 C. during the period wherein a considerable proportion of crotonic aldehyde is present.

I have found that there is a considerable formation of high-boiling products when butyraldehyde and butyl alcohol are in contact under certain conditions notincluding the presence of hydrogen. Thus, if butyraldehyde and butyl alcohol produced by processes other than hydrogenation and distilling without high-boiling residues, are mixed together and the mixture subjected to fractional distillation, there will be left a residue of high-boiling material similar to that encountered by early workers in the hydrogenation of orotonic aldehyde. If however, water is added to the mixture of butyraldehyde and butyl alcohol before heating it, it is possible to distil the aldehyde fractionally, together with a portion of the water, leaving the alcohol with the rest of the water, and then to dehydrate both the aldehyde and alcohol by usual methods, all without the formation of serious quantities of high-boiling products. In view of these facts, it is my belief that the improvement noted when steam is present in the hydrogenating zone is due chiefly to the fact that the steam passes on with the hydrogenation products and is condensed with them, the resulting water being present when the products are fractionally distilled.

While it is impossible for me to state exactly how the water acts to prevent the formation of undesired high-boiling products, there are two explanations 7111011 I consider plausible, as follows:

(1) The presence of water reduces the temperatures during the part of the distillation wherein bot-h butyraldehyde and butyl alcohol are present, and this tends to inhibit their interaction.

(2) Dibutyl butylal is a condensation product, formed by the elimination of water and the initial presence of water should hinder its formation pursuant to mass action principles.

In accordance with the foregoin I prefer to hydrogenate in the presence 0 a minimum quantity of water, the hydrogenation being effected in a plurality of more or less distinct zones of progressively increasing temperatures if a high yield 01' butyl alcohol is desired. If butyraldehyde is the desired product, only one zone, maintained at a modcrate temperature and corresponding to the initial zone of the series ust referred to, is

- employed. It will be understood that the water.

plurality of zones referred to may be successive portions of the same tube or passage, maintained at appropriate progressively iiicreasing temperatures.

The addition of water (meaning here n liquid, or vapor at or above the equilibrium temperature with liquid) isdcterrcd until the hydrogenation is substantially complete in order to insure a rapid hydrogenation. To minimize interaction between the butyl-aldehyde and butyl alcohol, the water is preferably added immediately after the hydrogenation.

In order to secure a rapid cooling of the mixture issuing from the hydrogenating apparatus, thereby minimizing the possibility of interaction between its components, the water is preferably introduced into the hot products as a spray of liquid. i i

While I prefer to exclude water from the hydrogenation zone, the presence of water therein is by no means precluded. Because of its diluting action, the water content of the mixture should be kept low, but in most instances the cost of removing any small amount of water contained in the crotonic aldehyde will not be justified by the increase in the rate of hydrogenation secured by such removal. In a usual method for the production of crotonic aldehyde, aldol is decomposed, giving a mixture containing about crotonic aldehyde and about 20% of This product separates itself into two layers: an upper layer containing about 93% of crotonie aldehyde and a lower layer containin about 20% of the aldehyde, the balance oii'each layer being water. Good results are obtained by utilizing the upper layer, as a whole or after the removal of such quantities of water as is economically feasible, as the material to be hydrogenated. In this case as in all others falling within my invention, the quantity of water present during hydrogenation will be materially. less than that which is most efl'ective in preventing the formation of high-boiling substances, and water will therefore be added after hydrogenation.

In a specific example, crotonic aldehyde in vapor phase and at about 115 C. was mixed with about five volumes of hydrogen and the mixture passed through a nickel catalyst at about 135 C. and of such extent that substantially all the crotonic aldeh do was hydrogenated. The mixture containing almost the theoretical yield of butyraldehyde and butyl alcohol in the proportion of about two ineinei parts ofthe former to one part of the alcohol, was then passed over a nickel catalyst at about 175 C. until the mixture contained about 4 parts of alcohol to one part of aldehyde. 70

A spray of water in the proportion of about one part to two parts of the combined aldehyde and alcohol was introduced into the mixture issuing from the second hydrogenating apparatus, and the entire mixture passed to a water-cooled condenser. The hydrogen was returned to the process and the condensate fractionally distilled at barometric pressure to separate the aldehyde from the alcohol. The compounds thus separated were dehydrated by usual methods. The yield of combined aldehyde and alcohol was slightly greater than 95% of the theoretical and about four parts of alcohol were produced for each part of aldehyde.

While I prefer to ell'ect the hydrogenation at substantially barometric pressure, the use of other pressures is not precluded.

I claim:

1. Process of hydrogenating crotonic aldehyde and fractionally distilling the reaction )I'OdllCt, which comprises adding water after ydrogenation and before distillation.

2. Process which comprises hydrogenating erotonie aldehyde in the presence of less water than is necessary substantially to revent the formation of undesired high-boi ing substances during subsequent distillation of the reaction product, making u the necessary amount of water by suita le addition after the hydrogenation and then distilling the reaction product. v

3. Process which comprises hydro enatin crotonic aldehyde in the absence 0 enoug water materially to retard the hydrogenation, adding water to the reaction mixture and distilling the latter, the water being added in such quantity that the formation of undesired high-boiling products during distillation is substantially prevented.

4. Process of hydrogenating crotonic aldehyde which comprises treating the aldehyde with hydrogen at a temperature below 140 C. until most of the crotonic aldehyde has been converted into saturated compounds 115 containing the propyl group; and then treating the product with hydrogen at a temperature above 140 C. to produce butyl alcohol.

5. Process of hydrogenating crotonie aldehyde which comprises treating the alde- 120 hyde with hydrogen at a temperature below 140? C. until most of the crotonic aldehyde has been converted into saturated compounds containing the propyl group; and then treating the product with hydrogen at 125 a temperature between 170 C. and 180 C. to produce butyl alcohol.

6. Process of hydrogenating crotonic aldehyde which comprises treating the aldehyde with hydrogen at a temperature below 130 140 C. until most of the crotonic aldehyde has been converted into saturated compounds containing the propyl group; and then treat ing the product with hydrogen at a temperature above 140 C. to produce butyl alcohol, the hydrogenation being effected in the presence of less water than is necessary substantiall to prevent the formation of undesired igh-boiling substances during subsequent distillation of the reaction mixture.

7. Process of hydrogenating crotonic aldehyde which comprises treating the latter with hydrogen at a temperature below 140 C. until most of the crotonic aldehyde has been converted to saturated compounds containing the propyl group; and then treating the product with hydrogen at a higher temperature to produce butyl alcohol; both said treatments with hydrogen being carried out in the resence of less water than is necessary e ectively to prevent the formation of undesired high-boiling substances during subsequent distillation of the reaction product; making up the necessary amount of Water by suitable addition after the hydrogenation; and then distilling the reaction product.

8. A process for the purification of butyric aldehyde consisting in distilling the aldehyde in the presence of sufiicient water to form a constant-boiling mixture with the aldehyde.

9. A process for the purification of normal butyric aldehyde consisting in distilling the aldehyde in the presence of suflicient water to form a constant-boiling mixture with the aldehyde.

10. A process of separating butyraldehyde from its mixtures with butyl alcohol which comprises distilling off the aldehyde, and providing and maintaining a content of water in the liquid residue throughout the distillation.

In testimony whereof, I afiix my signature.

HIRAM CHESTER HOLDEN. 

